With miniaturization of variable resistance memories, distances between adjacent memory cells can be shortened, and thus mutual interference between the adjacent memory cells can be problematic. The mutual interference between the adjacent memory cells can be a cause of an erroneous operation. For example, in phase-change memories in which resistivity of a high resistance state is relatively low, it can be desirable to prevent mutual interference between memory cells and stabilize characteristics of the memory cells.
In variable resistance memories, to change the variable resistance layer from a low resistance state to a high resistance state (a reset operation) or change the variable resistance layer from a high resistance state to a low resistance state (a set operation), a current with a predetermined current density may be directed to the variable resistance layer. In particular, in phase-change memories, a high current density may be used for a reset operation. When the current density is insufficient, a reset operation can become unstable. It can be desirable to realize the stable reset operation and stabilize characteristics of memory cells.